Effective Long-Term Stucco Waterproofing

Stucco is an attractive building material, creating both a natural and an elegant feel when used as a siding. Over the last several years, however, many are thinking twice about using stucco siding due to the extensive damage caused by wall rot to many homes in Southeastern Pennsylvania. In fact, stucco is intrinsically water resistant, but the lack of knowledge and craftsmanship of many of the contractors who are currently installing it have given it a bad name.

To achieve a tight, nearly waterproof seal that lasts, stucco installation needs to encompass three components: A multilayer application of the stucco and other materials, the use of an air gap between the layers, and the proper utilization of flashing around any openings in the façade. Knowing the right method of stucco installation will help you to select an experienced contractor and avoid the wall rot issues that have plagued so many in our area.

The Basics: Multiple Layer Stucco Installation

The prepping for the application of stucco is actually the most important element in creating a façade that can hold up to rain and moisture. With plywood or OSB as a starting layer, a stucco wall should be built out as follows.

  • Single layer of weather resistant barrier (WRB), such as asphalt paper or Grade D paper
  • 3D plastic drainage matrix to create an air gap
  • Another layer of WRB
  • Lath, which is a metal or fiberglass mat
  • 3 layers of stucco

The weather resistant barrier will go a long way towards blocking moisture from entering in the first place, but it is not foolproof. If and when moisture finds its way into the walls of your home, there must be sufficient aeration to allow it to escape.

Drainage Matrix (AKA Drainage Mat, Air Gap, or Rainscreen Gap)

The drainage matrix works hand in hand with a weep screed at the lower edge of the walls to create a gap that allows trapped moisture to escape from behind the walls. It also allows for evaporation due to the increased airflow it creates. The drainage matrix has a further advantage in helping to prevent moisture from spreading to the surrounding layers when it is combined with a weather resistant barrier.

Stucco installations that lack an air gap are the culprit in so many of Pennsylvania homeowners’ extensive issues with wall rot. Some home inspectors are advocating to make the use of a drainage matrix a required part of the state’s stucco installation requirements. As a consumer, it is important to seek out a masonry company that employs a drainage matrix in their stucco installations.

The Purpose of Flashing

Flashing is a waterproof material—aluminum, steel, PVC—that is used to keep water out of any openings in the stucco, such as where windows and doors are placed or at the intersections between stucco and roof. However well your walls are constructed, if flashing is not utilized, and utilized properly, you will eventually have a problem with moisture intrusion.

Metal flashing is used to create an impenetrable barrier around the openings where doors and windows are installed. Several layers of WRB paper should be used below the bottom window flanges and at the sides in conjunction with flashing in order to get the best result.
Depending on the design of your roof, there may be areas where the roof does not project out beyond the stucco wall or where the stucco meets the roof. Kick-out flashing, a type of metal flashing specifically designed for these areas, will prevent water from entering and ultimately leading to wall rot. WRB paper applied at the soffit line and along the upper edge of the wall will help as well. Strategically placed rain gutters may increase the effectiveness of all of these measures.

Maintenance and Care

Ensuring that your masonry installation is done by knowledgeable professionals is more than half the battle. As with the interior of your home, though, keeping tabs on any signs of wear and tear is important. Be on the lookout for discoloration and for any cracks that may appear over time so that they can be investigated and repaired. This will extend the life and appearance of your stucco siding. Remember that stucco should not be pressure washed as it may well introduce excess water into the walls—find the cause of the discoloration instead.

Stucco Installation—The Right Way

Stucco Today has 30 years of experience installing and remediating stucco work in Southeastern Pennsylvania. We’ve built our reputation on doing the job the right way the first time—that’s why we’re able to guarantee all of our work for 5 years after the project is complete.
It’s important to thoroughly vet any masonry contractor who intends to install stucco on your home’s façade. Using all the recommended layers in preparing the surface, employing a drainage matrix, and correctly utilizing flashing will ensure that your home is structurally stable and beautiful for many years to come, protecting you and your investment down the road.

Call us at Stucco Today to discuss new projects or an existing installation that may require remediation. Trust only the area’s best for your home!

Schedule an inspection of your home’s siding or request a quote today!